African Americans are disproportionately affected by HIV/AIDS. Although they comprise only 13% of the US population, African Americans account for nearly half of the people diagnosed with HIV/AIDS. As compared to other races/ethnicities, African Americans with HIV/AIDS have shorter survival times and more deaths (CDC, 2009). Although a number of factors are associated with these disparities, clear underlying causes remain elusive. Moreover, African Americans and other racial/ethnic minorities are at heightened risk for low health literacy. Low health literacy among African American AIDS patients has been implicated as a contributing factor to disparities in medication adherence. An important component of traditionally defined adherence (pill- taking frequency), is medication management or "concordance" between patient and provider regarding a medication regimen. Concordance includes correct pill identification, comprehension of the number of doses/pills per day and the timing of doses as well as accurate interpretation of warning labels, food intake instructions. Our team found that poorer management (concordance) of a simulated HIV regimen among African Americans was mediated by low health literacy and numeracy (Waldrop-Valverde et al., 2010). Although there has been a proliferation of studies on the effects of poor adherence on clinical outcomes in HIV patients, comparatively little study has been conducted on the relationship of concordance to HIV clinical outcomes. Support for the importance of disentangling adherence from concordance is emerging among other health conditions (e.g., anticoagulation control, diabetes) and vulnerable populations (e.g. elderly). To our knowledge, however, no studies have tested medication discordance as a cause of disparate health outcomes. Medication discordance may go unnoticed in routine clinical practice since adherence assessment is often limited to only measures of dosing frequency. Therefore, the magnitude of the problem of medication discordance in HIV is not well understood nor how it may impact disease progression and clinical outcomes. We suggest that medication discordance may be a root cause of health disparities among African Americans with HIV/AIDS and propose to test the hypothesis that low health literacy leads to medication discordance and, subsequently, to poorer HIV-related clinical outcomes for African American HIV/AIDS patients. As part of our primary model testing health numeracy/literacy mediated medication management and clinical outcomes, we will also include additional patient and system contributors to health disparities from medical sociological literature to develop a comprehensive model that represents the complex interaction of risk and protective factors for those with limited health literacy. Study aims will be tested in a sample of 600 HIV/AIDS patients stratified by race/ethnicity and followed for 6 months. PUBLIC HEALTH RELEVANCE: Although a number of studies have examined underlying causes and associated risks for disparate disease outcomes among African Americans, far fewer studies have investigated the role of health literacy and specific health-promoting behaviors on health disparities, within the context of broader social, structural and economic realities. Through its innovative approach, this study will demonstrate the effect of poor functional health literacy on disparate health outcomes and improve conceptual knowledge of health literacy in relation to other individual and contextual variables that also shape disparities. Eliminating health disparities is a primary goal of the DHHS and this highly significant study will directly impact efforts to improve parity among our most vulnerable populations.